Half the cattle have been shot and the remainder quarantined amid concern about the contamination of other animals in the remote region about 900km south-east of Darwin.

The McArthur River mine (MRM) is one of the world's largest producers of lead, zinc and silver.

My concern is that we've tested cattle and we've looked at cattle but there are other types of animals and organisms that use and feed off that river. Who's to say what the levels of contamination in those species are?

"It's an indictment on that company's ability to be transparent with its stakeholders in the community - for me that's of great concern."

He said he was expecting information from a FOI request into the mine on Monday and that it was a "staggering coincidence" the department had made the announcement today.

He also said his clients in the nearby town of Borroloola had not been told about the contamination, even though the department has known for the last year.

"As far as I'm aware they haven't been told about this," he said.

"The government representative today said all stakeholders had been told."

"My concern is that we've tested cattle and we've looked at cattle but there are other types of animals and organisms that use and feed off that river.

"Who's to say what the levels of contamination in those species are?"

Asked to respond to the EDO's allegations, mine owner Glencore said the mine was located on a pastoral lease that ran about 17,000 head of cattle.

"A large part of our cattle management plan focuses on fencing in and around areas near the mining operation and sites of cultural significance to the local Indigenous community such as Barramundi dreaming," a spokesperson said in a statement.

"We will continue to work with the Government on our cattle management plan. In addition to this, mustering is conducted on a regular basis to remove cattle from site."

"As most Territorians know maintaining fencing during the wet season is a huge challenge with floods taking out fences each year. MRM is also taking advice on how to construct fencing in the river and creek channels to better withstand wet season rains."

The NT Cattlemen's Association (NTCA) said it was the Department of Mines and Energy responsibility to make the information public.

"This recent incident further reinforces to us the requirement for mandatory access agreements between the pastoral industry and the mining industry," NTCA CEO Tracey Hayes, said.